Lithium-ion batteries are found in a fast-growing number of products, from consumer electronics, such as cell phones, PDAs and laptops, to electric vehicles, airplanes and aerospace equipment. As one of the most popular types of rechargeable battery for portable electronics, lithium-ion batteries have superior energy densities, no memory effect, and a slow loss of charge when not in use. Lithium-ion batteries are becoming a common replacement for the lead acid batteries. A lightweight lithium/carbon negative electrodes and lithium iron phosphate positive electrodes are clearly favored over the heavy lead plates and acid electrolyte.
With significant advantages such as long cycle lifetimes and relatively high specific capacities, the lithium-ion battery is becoming a prevailing energy storage technology. Its development has benefited from the discovery of key new electrode materials, including graphite and LiCO2 acting as an anode and a cathode, respectively. (Kazunori, et al. 1994 Solid State Ionics 69, 212-221.) These materials often exhibit a layered structure, which allows for Li+ insertion and extraction with minimal influence on the host structure, thereby enabling long cycle lifetimes. (Tarascon, et al. 2001 Nature 414, 359-367.) The measured specific capacities of these materials, however, are limited by their chemical nature and now fail to meet the ever-growing needs. (Armand, et al. 2008 Nature 451, 652-657.) In comparison, high-capacity materials lacking a layered structure, such as Si, Si-alloys, Sn, and SnO2, suffer from short cycle lifetimes due to structural degradations caused by Li+ insertion and extraction. (Kim, et al. 2008 Angew. Chem., Int. Ed. 47, 10151-10154; Hu, et al. 2008 Angew. Chem., Int. Ed 47, 1645-1649; Chan, et al. 2008 Nat. Nanotechnol. 3, 31-35; Kasavajjula, et al. 2007 J. Power Sources 163, 1003-1039; Wolfenstine, et al. 2003 J. Power Sources 124, 241-245; Liu, et al. 2007 J. Electrochem. Soc. 154, A97-A102; Roberts, et al. 2002 J. Power Sources 110, 424-429; Deng, et al. 2009 Angew. Chem., Int. Ed. 48, 1660-1663; Yu, et al. 2009 Angew. Chem., Int. Ed. 48, 6485-6489; Park, et al. 2007 Angew. Chem., Int. Ed. 46, 750-753; Paek, et al. 2008 Nano Lett. 9, 72-75.)
Thus, a critical unmet need remains for novel layered materials with high specific capacities should therefore be important in the development of lithium-ion battery technology.